Studies of spatial hearing will rely primarily on psycho physical measures made in a unique facility called the Simulated Open Field Environment (SOFE). The SOFE uses computer controlled loudspeakers in an anechoic chamber to create realistic auditory scenes with simulated sources and echoes. In addition, a projected visual scene allows for study of relations between hearing and vision. Studies include fusion of cues in reverberant environments, auditory motion and visual capture in localization. Both blind and sighted subjects arc studied. A second direction studies how information is retrieved when a perceiver must share attention between two sources. The guiding model says that differential use of two memory systems, one peripheral and one more cognitive, determines when there is a cost of shared attention. Data come from a variety of psycho physical judgments where subjects monitor and respond to two simultaneously presented dimensions. Work on both spatial perception and shared attention will be tested through measurement of brain activity in a functional Magntic Resonance Imager. For example, potential differences will be found between blind and sighted listeners in an auditory spatial task and different sites of activity will be compared during attentional tasks chosen to tap peripheral and central memories, respectively. It is expected that work on spatial perception is important for NIH interests functional disorders that involve directional hearing, that work on shared attention will related to interests in deficits caused by disfunctional memories, and that comparisons between blind and sighted subjects will aid in a long term goal of this grant to study and develop better auditory displays for conveying complex information to blind individuals.